Detecting Alzheimer’s early,
even before symptoms appear
, is one of the big topics at the Alzheimer’s Association's International Conference now taking place in Paris. The subject has also been the focus of a number of scientific research papers in recent months. NBC's chief science and health correspondent Robert Bazell explains the benefits and limits of early detection, available treatments for dementia and whether people with a family history want to know their risks.

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Q: Is it possible to tell whether someone who has no symptoms now is going to get Alzheimer's in the future?
A: The simple answer is no. It is not possible.

Q: Then why is there so much discussion of the subject?
A: Many research groups are developing methods that may soon help predict risk of Alzheimer’s disease. These include brain scans with radioactive markers that detect the level of amyloid, a protein in the brain associated with Alzheimer’s. Taps of the cerebral spinal fluid can also measure the level of amyloid and, possibly, so can an experimental examination of the small blood vessels in the eye.

Another type of brain scan measures the size of the hippocampus, a region of the brain that shrinks as Alzheimer’s sets in. Researchers are also are working on simple blood tests that may detect amyloid. It will take years more of testing asymptomatic people and then carefully following them over time to know how accurate the tests are.

Q: What is the use of these tests now?
A: They help doctors better determine whether someone who has the signs of Alzheimer’s actually has that disease and not some other form of dementia which may be treatable. They can also predict with very good precision which people who have the pre-Alzheimer’s condition called mild cognitive impairment (MCI) are likely to progress to full-blown Alzheimer’s.

Q: With such limited use, why is so much effort going into Alzheimer's early detection?
A: The big hope is that by identifying people early, doctors will be able to stop the disease from developing in the first place or, at least slow it, considerably. The prevailing belief now is that Alzheimer’s develops over a period of decades and many scientists believe it may be possible to treat it only by starting therapy with some drug years before anyone has symptoms. It will likely take many years to prove this hypotheses.

Q: Why would someone with mild cognitive impairment (MCI) want to know if they are getting Alzheimer's?
A: Some don’t want to know, but others and their families want to start making preparations for the awful road ahead while the patient's mind is still relatively intact.

Q: Are there any drugs that can slow the progress from MCI to Alzheimer's?
A: Unfortunately there are no such drugs. There are drugs on the market — Aricept is the most popular — that elevate cognitive function in some patients for a brief periods, but none stops the inevitable decline. Many trials are underway to try to find drugs to slow the progression of Alzheimer’s, but none has yet achieved success.

Q: What can the tests do for someone who has no symptoms?
A: The tests can tell if someone has an increased risk of Alzheimer’s, but they cannot say for certain they will get the disease.

Q: With that limit and without effective drugs, are there still people who want to get tested?
Yes, Alzheimer’s specialists tell me that while most people don’t want such information, there are those — especially people with a strong history of Alzheimer’s in their family — who are asking for and getting the testing even though it provides an inconclusive answer.